Insulated strain rod



lJuly 29 1.924. 1,502,829

W. H.KEMPTON I NSULATED STRAIN ROD Filed March 13. 1918 Y /0 ffy.

, WITNESSES:

l va o -g I 2 INVENTOR M1441 BZY Q @c ATTORNEY Patented July 29, 1924.

UNITED STATES PATENT OFFICE.

WILLARD H. KEMPTON, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T WESTING HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVAN IA.

INSULATED STRAIN ROD.

Application filed 'March 13, 1918. Serial No. 222,195.

To all whom 'it may concern:

Be it known that I, WILLARD H. KEMr'roN, a citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Insulated Strain Rods, of which the following is a specification.

My invention relates to strain rods or insulators and it has for its primary object the provision of strain rods of an improved type which may be manufactured rapidly and at relatively low cost.

I-Ieretofore, most strain rods have been formed of wood, such as hickory. These rods have been largely used in tying together the parts of reactance and transformer coils where metal rods could not be used on account of the danger of short circuits through them, and also as strain insulators in the electriiication of steam railways and in the construction of ordinary trolley-line systems. In order to insure sufficient strength for service conditions, it has been found necessary to provide the ter.

minals of wooden rods with special coarse threads and with correspondingly threaded nuts. However, wooden strain rods are not entirely satisfactory because they sooner or later absorb sufficient moisture to cause them to burn out if subjected to the working line voltage, particularly in electrified-steamroad service where a voltage of 11,000 or more is employed.

By my invention I overcome these various objections by providing a strain rod having an insulating body portion which is not affected by moisture and having metallic connecting portions of such character that screw threads of the usual type and correspondingly threaded nuts may be employed.

' lCorresponding reference numerals refer to the same parts both in the ,description and in the various figures of the drawing in which Fig. 1 is a side elevation of a. strain rod, constructed in accordance with my invention; Fig. 2 is a similar view but showing the outer sleeve in section; Fig. 3 is a side elevation, partly in section, of a modified form of strain rod; Fig. 4 is aside elevation of another modified form of strain rod or insulator; Fig. 5 is a similar view the strain rod shown in Fig. 4 but showing the sleeve in section; Fig, 6 is a side elevation partly in section, of a still further form of strain rod', Fig. 7 is a side elevation, partly in section, of another strain rod and Fig. 8 is a side elevation of still another rod.

Broadly speaking, my improved strain rod or insulator consists of a tube or sleeve, of iibrous material united by a suitable binder, enclosing an intermediate spacing element of wood or other non-conducting material and terminal connecting elements which project beyond the ends of the sleeve. The sleeve may be composed of any suitable fibrous material and any proper binder, and the intermediate spacer element may also be of any suitable insulating material and the terminal connecting elements may be of any desired metal and of any suitable shape.

Preferably, however, the tube or sleeve is composed of fibrous sheet material, such as paper, and a phenolic condensation product, as an impregnating binder, which is render ed hard and water-proof by the application of heat and pressure.

In Figs. 1 and 2 I have illustrated a strain rod which comprises an insulating sleeve or body 10, an enclosed spacer element 11, of wood, and connector elements 12. The sleeve 10 is composed of a plurality of convolutions or laminations 13 of impregnated paper or other suitable librous sheet material and the spacer element 11 is made of wood. The connector elements 12 are shown as metallic studs, threaded throughout their lengths and having their inner ends in engagement with the ends of the spacer element within the ends of the sleeve and their oluter ends projecting beyond the ends of the s eeve.

The material of the sleeve is forced into i locking engagement with the threads, as shown, in a manner which will be later eX- plained, so that the studs are iirmly anchored in place. Obviously, instead of threading the studs for engagement with the sleeves, they may be roughened or otherwise formed to insure non-detachable en-d gagement with the` sleeve. Also, the outer ends of the studs, instead of being threaded, may be bent into the form of eyes or hooks.

If desired. the 'strain rod may be modified, as shown in Fig. 3, by molding a cover 14 of any suitable insulating moldable material or composition such as those having for a binder Shellac or similar gums, or those hav,

ing condensation resins as a binder and asbestos or the like as the fibre or filler. The cover 14 will preferably be ribbed circumferentially, as shown, and may extend over a part or the entire length of the body of the strain rod, its purpose being to increase the surface insulation of the device.'v

4In Figs. 4 and 5 of the drawing, I have shown a modified form of strain rod comprising a sleeve or body 15, of insulating material, enclosing a spacer block 16, of wood, and the threaded shanks 17 of anchoring elements 18, the exposed ends of which are in the form of eyes. The two types .of strain insulators are substantially identical, except as regards dimensions, the spacer element and sleeve of the form shown in Figs. 1 and 2 being relatively long and adapted for high-voltage service, while the spacer element and sleeve of the form shown in Figs. 4 and 5 are relatively short, although the sleeve is preferably of greater thickness; this form being adapted for lowvoltage service.

When making the form of strain rod shown in Figs. 1 and 2 I preferably take a sheet of paper, or other suitable fibrous material, previously impregnated with the desired binder, such as a phenolic condensation product, and wind it, by hand, about the spacer element 11 and the inner ends of the connector elements 12, the latter being positioned against opposite ends of the spacer element at the start of the winding operation. When the parts of the strain rod have been assembled in this manner, the entire rod is placed in a suitable mold and subjected to the combined action of heat and pressure. Under these circumstances, the binder softens and iiows into all spaces so as to insure `an intimate engagement between the iibrous sleeve and the other parts of the structure. The mold is then cooled, if the binder be of such a nature as to harden upon cooling, or, if the binder be of a phenolic condensation product, the heating continues until the binder is solidiiied, after which the mold is cooled.

The strain-rod structure shown in Figs. 4 and 5 may well be constructed by rolling fibrous sheet material, such as paper impregnated with a suitable binder, about a removable cylindrical mandrel, of suitable dimensions, to provide a tube of considerable length and the' desired diameter and thickness. This winding may be done either with or without the application of heat and pressure but, if heat is employed, it should be for only a sufficient period to slightly soften thel binder and not long enough to transform it to its solid state.

From the tube, thus formed, I cut pieces ofthe proper length to form sleeves 15 and into these sleeves I slip iirst the spacer blocks 16 and then the threaded or otherwise roughened ends of the connector elements 18. The strain rods, so assembled, are then placed in molds and treated in the manner previously described in connection with the strain rod shown in Figs. 1 and 2.

It will, of course, be apparent that the strain rods shown in Figs. 1, 2 and 3 may be made in the same manner as those shown in Figs. 4, 5 and 6 or that the method employed in constructing the strain rods of Figs. 1, 2 and 3 may be followed in constructing those of Figs. 4, 5 and 6. Obviously, inasmuch as the insulating sleeves are eX- tremely strong, tough and unaEected by moisture, the strain rods possess unusual mechanical strength. Furthermore, inasmuch as the spacer elements 11 are of wood and the sleeves, of fibrous material impregnated with a binder, are good insulators, reliable electrical properties are assured.

Ifv desiredtthe type of strain rod illustrated in Figs. 4 and 5 may be modiiied as shown in Fig. 6 by applying concavo-convex discharge guards 19 of metal against the ends of the body, these guards being held in place by eye-nuts 20 threaded upon the Shanks of the connector elements 19.

In Figs. 7 and 8, I show suspension insulators or strain rods the same in construction as that of Fig. 6 except that a porcelain guard 21 is mounted at the top in Fig. 7 and one at the top and one at the bottom in Fig. 8, washers 22 being interposed to form ti ht joints. In each instance, the guards are isposed with their convex faces uppermost so as to shed moisture, as well as to increase the surface insulation of the strain rod.

Although I have illustrated and described my invention in detail, it will be appreciated that the material of the spacer elements, the material of the connector elements, the fibrous material and the binder employed may be changed; that the shape and proportions may be altered and that the method of making the strain rods may be varied without departing from the spirit of my invention. I wish it understood, therefore, that no limitations, other than those set forth in the claims, are to be imposed upon my invention.

I claim as my invention:

1. A strain insulator including a pair of connector elements, a spacer element interposed between the connector elements, and a sleeve, formed of a sheet offibrous material impregnated with a phenolic condensation product as a binder wound into tubular form, the sleeve being molded. about the spacer element and adjacent ends of the connector elements.

2. A method of forming a strain insulator that comprises winding a sheet of ibrous ends of the tube section, and subjecting the material impregnated with a phenolic conarticle, so assembled, to heat and pressure l densation product as a binder about a. manin a mold. l

drel to form a tube, removing the mandrel, In testimony whereof, I have hereunto 5 cutting olI a section of suitable length from subscribed my name this 28th day of Feb.

the tube, insertin a s acer element of non 1918.

conducting material wlthin the tube section, inserting ends of connector elements into the WILLARD H. KELPTON. 

